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All Journal Majalah Forum Teknik UGM OPSI Green Engineering: Journal of Engineering and Applied Science
Trismi Ristyowati
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Agriculture, Biological Sciences & Forestry Civil Engineering, Building, Construction & Architecture Electrical & Electronics Engineering Engineering Industrial & Manufacturing Engineering

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PERANCANGAN SISTEM KERJA UNTUK MENINGKATKAN HASIL PRODUKSI MELALUI PENDEKATAN MACROERGONOMIC ANALYSIS AND DESIGN DI SENTRA INDUSTRI BATIK AYU ARIMBI SLEMAN Trismi Ristyowati; Tri Wibawa
OPSI Vol 11, No 2 (2018): ISSN 1693-2102
Publisher : Jurusan Teknik Industri Fakultas Teknologi Industri UPN "Veteran" Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (510.22 KB) | DOI: 10.31315/opsi.v11i2.2553

Abstract

MINIMASI WASTE PADA AKTIVITAS PROSES PRODUKSI DENGAN KONSEP LEAN MANUFACTURING (Studi Kasus di PT. Sport Glove Indonesia) Trismi Ristyowati; Ahmad Muhsin; Putri Puji Nurani
OPSI Vol 10, No 1 (2017): ISSN 1693-2102
Publisher : Jurusan Teknik Industri Fakultas Teknologi Industri UPN "Veteran" Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (580.249 KB) | DOI: 10.31315/opsi.v10i1.2191

Abstract

PT Sport Glove Indonesia merupakan perusahaan manufaktur yang memproduksi sarung tangan yang beralamat di Krandon Pendowoharjo, Sleman, Yogyakarta memiliki karakteristik make to order dalam proses produksinya. Dalam pemenuhan order harian, perusahaan sering tidak dapat mencapai target produksi, dikarenakan adanya pemborosan dalam proses produksi yang berupa cacat dan delay, sehingga dalam pemenuhan target produksi harian memerlukan waktu yang panjang, yang akhirnya melewati batas waktu dan target belum tercapai. Untuk itu penelitian ini bertujuan meminimasi wate aktivitas proses produksi agar target pemenuhan order apat tercapai.Dalam upaya pemenuhan order tersebut, perlu adanya perbaikan pada proses produksi, salah satu pendekatan yang digunakan untuk perbaikan ini adalah meminimasi sumber-sumber waste yang ada. Lean manufacturing merupakan pendekatan untuk mengefisiensi sistem dengan meminimasi pemborosan (waste). Pendekatan ini dilakukan dengan cara memahami aliran informasi dan fisik pada lantai produksi yang dibuat dalam bentuk visual dalam bentuk value stream mapping.Usulan perbaikan yang diberikan untuk meminimasi adanya waste cacat dan waiting pada proses produksi sarung tangan golf di PT Sport Glove Indonesia adalah penambahan pekerja pada proses jahit, kegiatan maintenance dalam bentuk preventive maintenance, melakukan pengawasan dan pengarahan kepada pekerja, dan memberi pelatihan kepada pekerja untuk meningkatan dan menyetarakan ketrampilan dan standar kerja.
PENJADWALAN PROYEK DENGAN PENERAPAN SIMULASI MONTE CARLO PADA METODE PROGRAM EVALUATION REVIEW AND TECHNIQUE (PERT) Widya Nurul Shofa; Irwan Soejanto; Trismi Ristyowati
OPSI Vol 10, No 2 (2017): ISSN 1693-2102
Publisher : Jurusan Teknik Industri Fakultas Teknologi Industri UPN "Veteran" Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (608.284 KB) | DOI: 10.31315/opsi.v10i2.2110

Abstract

PT At Taqwa Sejahtera has implemented of residential development that duration about 152 day. Due to delay in the supply of primary raw materials, the processing time getting longer or not accordance to planning schedule on October 27, 2017. The project delay have impact on the company which will given punishment.The aim of this study research to the evaluate the project implementation schedule and project scheduling for more optimal time, with the best probability, and minimize the influence of the causes of delays to the project completion time. Project scheduling processing is done by using Program Evaluation Review and Technique (PERT) and implementation with Monte Carlo simulation using Ms Excel software.Based on data processing, the calculation of the project point accelerated time to 147 days with cost Rp 417.315.909,25 and probability of 63%, whereas with the application of Monte Carlo simulus the average conviction rate is at 156 days with cost Rp 402,310,654.25 and probability of 94%.  
Pengaruh Potongan Harga pada Sistem Inventori (Q,R) yang Mempertimbangkan Ketergantungan antara Lot Size dan Lead Time Nur Indrianti; Setya Prajoko; Trismi Ristyowati
Forum Teknik Vol 30, No 3 (2006)
Publisher : Faculty of Engineering, Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar

Abstract

This paper is concerned with lot size dependent lead times in a (Q,R) inventory system considering-quantity discounts offered by suppliers. With regards to the existing model that considers the impact of lot size on lead time and safety stock equirements, we present an efficient iterative algorithm to decide lot size that minimizes total inventory cost. The algorithm simultaneously determines lot size and safety stock based on the tradeoff between inventory holding cost and shortage cost. A nurnerical example is provided to clarify the iteration procedure. In addition, we identify the effict of shop floor queing factor on lot size decision.The result of the study shows that purchasing larger lot size does not always result in minimum total inventory cost. Larger lot size reduces per unit ordering cost and shortage cost, but increases the holding cost due to more inventories. Moreover, we conclude that increased shop floor queuing factor leads to increased production lead time, resulting in larger lot size.Keywords: (Q,R) inventory system, lot size dependent lead times, quantity discount.
Determination of Customer Order Decoupling Point (CODP) Based on Mass Customization Concept to Minimize Manufacturing Lead Time Yuli Dwi Astanti; Sadi Sadi; Deni Widiyanto; Puryani Puryani; Trismi Ristyowati
OPSI Vol 16, No 1 (2023): ISSN 1693-2102
Publisher : Jurusan Teknik Industri Fakultas Teknologi Industri UPN "Veteran" Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31315/opsi.v16i1.9679

Abstract

Make To Order (MTO) is a manufacturing strategy that executes different orders based on consumer demand. In the MTO strategy, products are produced only when there are orders from consumers. In this MTO system, the production process starts when an order arrives and starts with planning raw materials which takes a long time and causes a long lead time (MLT). Long MLT often causes production delays and forces companies to pay more overtime. Companies must adopt a production system that can fulfill a variety of orders and has a fast response time. In this research, a case study was conducted on a shoe and bag manufacturing company in the fashion industry. This study aims to implement a mass customization manufacturing (MC) strategy to minimize MLT. The MC strategy uses the concept of a production process based on orders and inventory. This study is expected to reduce MLT so that production delays do not occur again. The results of this study indicate that relocation of the customer order decoupling point (CODP) can reduce MLT from 30 days to 26 days. By reducing this, production delays can be overcome. In terms of costs, this production system is lower than before and the profits are higher.
Developing an Integer Linear Programming Model for Hotel Shift Scheduling: Empirical Insights from a Central Java Hotel Irwan Soejanto; Trismi Ristyowati; Indun Titisariwati
Green Engineering: International Journal of Engineering and Applied Science Vol. 2 No. 3 (2025): July : Green Engineering: International Journal of Engineering and Applied Scie
Publisher : International Forum of Researchers and Lecturers

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.70062/greenengineering.v2i3.221

Abstract

Employee shift scheduling in the hospitality industry remains a critical yet complex task due to fluctuating operational demands, fairness requirements, and labour regulations. Many hotels still rely on manual scheduling methods, which are time-consuming and prone to biases, particularly in ensuring fair workload distribution across employees. Despite numerous studies on workforce scheduling, limited attention has been given to integer linear programming (ILP) models that address gender-based restrictions and operational fairness simultaneously in real-world hotel contexts, especially in developing regions such as Central Java. This study proposes an Integer Linear Programming (ILP) model to generate optimal shift schedules for hotel staff over a 31-day planning horizon. The model incorporates operational constraints, including one shift per day, gender-based restrictions (which prevent female staff from working night shifts), availability, minimum staffing levels, and fairness in workload distribution. Key parameters and binary decision variables were defined to ensure compliance with the hotel's specific requirements. Empirical data were collected from a hotel in Central Java involving 20 employees, and the model was implemented using Python with a Gurobi solver. The ILP model successfully generated optimal schedules in under 10 seconds, significantly outperforming the manual method, which required over 4 hours. While the manual schedule resulted in an imbalance where some employees worked over 27 days and others only 22, the ILP approach enforced a strict maximum of 26 working days for all staff. Furthermore, the fairness index (FI) improved from 19.2% in the manual method to 0% in the ILP-generated schedule, indicating complete equity in workload allocation. The proposed ILP model demonstrates its effectiveness in improving scheduling fairness, operational efficiency, and compliance with labour policies. This work not only addresses a critical research gap in hospitality scheduling practices in Indonesia but also offers a replicable framework for other labour-intensive service sectors. Future research may explore multi-objective extensions incorporating employee preferences, satisfaction, and dynamic demand fluctuations.
Large neighborhood search for route and fleet optimization in frozen food distribution Simbolon, Jonathan Andrepa; Trismi Ristyowati; Soepardi, Apriani; Irwan Soejanto; Yuli dwi Astanti; Puryani; Chaeron, Mochammad
OPSI Vol 18 No 2 (2025): OPSI - December 2025
Publisher : Jurusan Teknik Industri, Fakultas Teknologi Industri UPN "Veteran" Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31315/opsi.v18i2.15743

Abstract

This study develops an optimization model to enhance the distribution efficiency of a frozen food distributor. The company faces operational inefficiencies due to excessive fleet capacity and conventional route assignment methods, which increase travel distances and overall distribution costs. To address these challenges, an extended Capacitated Vehicle Routing Problem with Time Windows (CVRPTW) model is proposed, which integrates heterogeneous fleet characteristics and prioritizes customer service constraints. The model is solved using the Large Neighborhood Search (LNS) metaheuristic to determine optimal routing and fleet allocation strategies. The optimized model achieves a 15.95% reduction in total travel distance and a 21.84% decrease in total distribution costs compared with the company’s current operations. The findings confirm the effectiveness of the LNS-based CVRPTW approach in improving logistics performance and provide practical insights for companies seeking to minimize distribution costs through strategic route planning and fleet management.
Co-Authors Ahmad Muhsin Apriani Soepardi Deni Widiyanto Indun Titisariwati Irwan Soejanto Mochammad Chaeron Nur Indrianti Nurul Khumaida Puryani Puryani . Putri Puji Nurani Sadi Sadi Setya Prajoko Simbolon, Jonathan Andrepa Widya Nurul Shofa Yuli Dwi Astanti